Watch the Add a Bassline & Hammers online guitar lesson by Vicki Genfan from Acoustic Rhythm Guitar Cookbook
Start with the Em and work on the hammer-on as well as getting that pinky up to the G on the 6th string. Decide how you want to finger the Em chord – which feels better to you?
For all the hammers, remember to keep the fingers that aren't hammering in the chord position. Practice the whole study slowly at first and make sure you're hitting the correct bass notes. The study requires quite a bit of movement between the 6th, 5th and 4th strings, as bass notes. In particular, pay attention to the change between the C chord and the B7 at the end of the progression. This is probably a new chord (B7) and there's a bit more movement involved when making this change from the C.